The present invention concerns task chairs having a reclineable back, and more particularly concerns chairs having a reclineable back and a forwardly movable/tiltable seat that move with a synchronous movement as the back is reclined, and that are pivotally interconnected in a novel manner.
Reclineable chairs have gained wide and enthusiastic support in the chair industry. Reclineable chairs often include a back frame pivoted by back pivots to opposite sides of a base or control housing to define a back-tilt axis. A problem is that the back pivots do not always align perfectly with the back-tilt axis. This misalignment can be a result from the back pivots being skewed at an angle to the back-tilt axis, or from the back pivots being parallel to the back-tilt axis but non-aligned with it, or from the back pivots changing orientation as a person sets in the chair or reclines in the chair. A net result is that, during recline of the back, at least one chair component must flex and mechanically give to prevent binding. Typically, either the control housing or back frame structure deforms, and/or the bearing is sloppy enough to compensate for the misalignment. If the deformation is large enough or if the chair components are not designed for such flexing, one of the chair components may break, fail, or fracture over time due to cyclical fatigue failure. Another problem is that bearings of the back pivots will rapidly wear from the high forces generated by the misalignment. This results in looseness in the back, which can be objectionable in some situations.
Another problem with known back pivots for chairs is that they can be cumbersome to assemble and/or manually intensive to assemble, as well as expensive, since holes must be aligned to receive pivot pins/axles, and the pivot pins/axles must be adequately but not overly tightened and secured. Specifically, during securement, the pivot pins/axles cannot be overtorqued or the assembly will bind, and also cannot be undertorqued or the assembly will be unacceptably loose and prone to come apart.
Similar problems can occur in synchrotilt chairs where a seat has spaced apart seat pivots that do not accurately align with a seat-tilt axis. It is noted that seat pivots must also support a large portion of the weight of a seated user, thus adding to their stress level.
Along with the above requirements, any back pivots and seat pivots must be integrated into the chair construction to provide an acceptable appearance, since they are often located in a highly visible area of a chair.
Accordingly, a chair construction solving the aforementioned problems is desired.